Field of the Invention
This invention relates generally to a passive entry and passive start (PEPS) system on a vehicle that employs a Bluetooth Low Energy (BLE) device (node) within the vehicle and, more particularly, to a PEPS system on a vehicle that employs one or more BLE nodes within the vehicle to determine whether a vehicle fob is within the vehicle or outside of the vehicle.
Discussion of the Related Art
Modern vehicles typically employ a key fob (FOB) that wirelessly transmits RF command signals to a vehicle controller to perform certain vehicle functions, such as lock the doors, unlock the doors, open the trunk, open the hatch, start the engine, turn on a security light, etc. The vehicle operator will press a particular push button on the FOB that typically has an image of the function that the button provides in order to transmit the command signal to the vehicle. The transmission is coded in such a manner that not only does the command perform a certain operation, but also protects the transmission from being recorded and resent by a third party. FOBs of this type have a limited range, and provide a convenience factor for the vehicle operator.
Modern vehicles also typically allow a vehicle driver to set various vehicle devices and systems, such as vehicle mirrors, seats, pedals, radio, etc., to a particular desirable setting, and then allow the driver to record those settings as pre-sets by activating a storing button. If the settings are changed from the last time the vehicle driver drove the vehicle, such as by another vehicle driver, then that vehicle driver can activate the pre-sets, such as by pressing the storing button or another button, so that all of the devices are returned to the desirable position for that driver. A signal transmitted from the FOB identifying the vehicle driver can be used to set the various vehicle devices and system to the pre-set conditions, where the particular FOB is unique to the vehicle driver.
As mentioned above, a typical system that allows a FOB to provide vehicle commands is activated by the vehicle driver or other authorized user using the FOB. In some vehicle designs, the vehicle performs the particular function automatically as the user approaches the vehicle, where the user is not required to actively transmit the signal. One known system, referred to as a passive entry passive start (PEPS) system, periodically interrogates or polls the area immediately around the vehicle to detect the FOB using a low frequency (LF) pulsed signal (30-300 kHz) transmitted from the vehicle at a predetermined pulse rate. The pulse width and the pulse rate of the polling signal are set based on how fast the user could be approaching the vehicle and how far from the vehicle it is desirable to first detect the user. When the FOB receives the low frequency pulsed polling signal, and authenticates it, the FOB will automatically transmit a command signal to the vehicle so that the vehicle will perform the particular function that is has been programmed to perform.
Low frequency signals are typically used for the FOB polling because they only radiate a short distance. Further, because of the short range of the low frequency pulsed polling signal, it is possible to interrogate directionally, such as at the left or right side of the vehicle or the front or rear of the vehicle. Thus, because the vehicle can know the direction of the approaching user, the vehicle need only open the door for that side.
Generating and transmitting low frequency signals typically requires a relatively large amount of current, such as on the order of about 700 mA for each pulse that is transmitted. Therefore, the amount of time that the PEPS system is able to provide the pulsed polling signal at the low frequency before the vehicle battery voltage is reduced to an unacceptable state-of-charge, below which the driver may not be able to start the vehicle, is relatively short, for example, on the order of 12-24 hours. When this time has passed since the last time the vehicle was started, the PEPS system will go into a sleep mode, and not be able to provide the polling signal.
In certain vehicle designs, because of the high energy use of the interrogation process, the system only “wakes-up” to provide the interrogation of the FOB when the user pulls on the vehicle door handle. Other designs have been proposed for a vehicle that allow a vehicle door handle to retract into the vehicle door for security purposes and upon detection of an authorized user will extend the handle to allow the driver to gain access to the vehicle. Current systems that deploy a vehicle handle from a retracted position may require about ten feet between when an authorized vehicle user is detected and when the user arrives at the vehicle to perform the operation satisfactorily. Another limitation of low frequency PEPS systems is that they require multiple low frequency antennas, such as five, which are relatively large and difficult to package.
In order to overcome this power limitation of PEPS systems, it has been proposed in the art to employ a BLE node integrated on the vehicle that is used to interrogate the FOB. Bluetooth device pairing is well understood by those trained in the art and can be accomplished by three methods, namely, ‘Just Works’, ‘Alphanumerical Key Entry’ and ‘Out of Band’ key exchange. In all three methods, the pairing devices exchange information including the exchange of private information that is only known to the pairing devices. This private information is used to establish connections in future encounters.
U.S. Patent Application Publication No. 2012/0158213, titled, Vehicle Data Services Enabled by Low Power FM Transmission, assigned to the assignee of this application and herein incorporated by reference, discloses a PEPS system that employs Bluetooth technology. The '213 application discloses a Bluetooth pairing process between a consumer's smart phone/consumer electronic (CE) device and a vehicle to secure the communications between the vehicle and the CE device and to determine if the CE device is an authorized device. For example, when pairing a CE device with a vehicle, the CE device and the vehicle exchange information known only to those two devices. The next time the CE device and vehicle are within the Bluetooth radio frequency range, the devices can automatically establish a Bluetooth session based on the private information that was previously shared between the devices. That is, the CE device and the vehicle exchange the private Bluetooth information over the FM frequency band. Thus, the CE device and the vehicle are able to verify/confirm that the CE device and vehicle are authorized devices. The private information can also be used to secure the data exchange between the CE device and the vehicle through encryption processes that uses the private information as an encryption key, which is well known to those trained in the art.
Employing low energy Bluetooth technology allows the vehicle to be parked for an extended period of time and still be operational to interrogate the FOB once it is within the vicinity of the vehicle. Further, since modern smart phones employ BLE technology, it is conceivable that future vehicles may not even require a FOB where the user's personal smart phone would be used instead.
One of the features of a PEPS system is to allow engine starts by pushing a button on the vehicle dashboard by an authorized user. In order to verify that the person pushing the button is an authorized user, the PEPS system must verify that the authorized FOB is within the vehicle at the time that the start button is pressed. A potential problem exists in that one authorized user may start the vehicle with the properly authorized FOB within the vehicle, such as a husband warming a vehicle for a wife on a cold day, where once the vehicle is started and the husband leaves the vehicle with the FOB, the wife may drive away the car without an authorized FOB. When this person reaches her destination and then wishes to start the car to return, she will not have the FOB to allow the vehicle start. Therefore, it is necessary that the PEPS system always knows whether the FOB is inside or outside the vehicle while it is running.
The current PEPS systems use the 125 kHz and an RSSI (received signal strength indicator) threshold to determine if the FOB is within the vehicle. Determining whether the FOB is inside or outside of the vehicle is straight forward for the low frequency PEPS system because the signal strength falls off quickly the farther the FOB is from the vehicle. Also, for the current PEPS systems, once the vehicle is running, power draw is no longer a concern and the PEPS system can continuously provide periodic interrogations of the FOB to ensure that it is still within the vehicle. However, BLE nodes operate at 2.4 GHz, which makes determining whether the FOB is within the vehicle or outside the vehicle very difficult by conventional RSSI threshold techniques. This is due to the fact that at these high frequencies, such as 2.4 GHz, the signal reflects off of various metallic objects and the RSSI fluctuates and oscillates over very short wavelengths (2-4 cm) depending on the signal reflections.